1. Field of the Invention
The present invention relates to a thermal object measuring apparatus for detecting a thermal object by using a pyroelectric sensor for detecting infrared rays, (in particular, heat rays) and a distance sensor using near infrared rays.
2. Related Art of the Invention
Recently there is a growing need for means of detecting a human body, without making any contact, in the field of air-conditioning, lighting, security and others.
As means for detecting human bodies existing in a space, various methods have been used or proposed so far, including a method of using a CCD camera to detect a human body from the obtained image, a method of detecting a human body by detecting an infrared ray using a guantum type infrared ray camera, and a method of detecting a voltage output generated while a thermal object moves by installing a Fresnel lens before the sensor, and by using an inexpensive pyroelectric type infrared ray sensor.
However, in the method using a CCD camera mentioned above, the detection algorithm for picking up a human body from the image is very complicated, the apparatus is huge, the processing time is long, and the system is very expensive. In the method of using the quantum type infrared ray sensor, the sensor must be cooled during operation, and the apparatus is large and expensive, so it is not practical for general use. The method of using the pyroelectric type sensor solves the problems of the size and price of the quantum type sensor, but a still human body cannot be detected, and errors are caused by wind or the like. By installing a chopper before the sensor, a still human body can be measured, but other heat sources having a similar radiation temperature and area may be mistook as a human body.
As a distance sensor for measuring the distance to an object, methods of using ultrasonic waves, millimeter waves, and laser radar are known. The method of using ultrasonic waves is practical at a distance of about 5 m, but at a further distance it is hard to enhance the directivity up to the precision required for detecting a human body. The methods of using millimeter waves and laser radar are actually used in the field of measuring the bumper-to-bumper distance of vehicles, but the apparatus is very large and expensive, and it is harmful to the eyes, and there were many restrictions for its use.